Guidelines for Canadian Drinking Water Quality

Copper compounds have been widely used in industrial processes and agriculture. As a result, elevated Cu concentrations can be found in certain areas of the biosphere. To better understand the toxicity of Cu to organisms it is necessary to understand the mechanism by which Cu influences biological and chemical processes in the environment. This review will examine Cu toxicity, microbial resistance mechanisms and factors influencing Cu speciation and toxicity in the environment

Copper toxicity and chemistry in the environment: a review

https://faculty.washington.edu/korshin/Class-486/JMM(49)31.pdf

Detection and enumeration of coliforms in drinking water: current methods and emerging approaches

Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

Atmospheric Movement of Microorganisms in Clouds of Desert Dust and Implications for Human Health

Investigations concerning the role of distribution system biofilms on water quality were conducted at a drinking water utility in New Jersey. The utility experienced long-term bacteriological problems in the distribution system, while treatment plant effluents were uniformly negative for coliform bacteria. Results of a monitoring program showed increased coliform levels as the water moved from the treatment plant through the distribution system. Increased coliform densities could not be accounted for by growth of the cells in the water column alone. Identification of coliform bacteria showed that species diversity increased as water flowed through the study area. All materials in the distribution system had high densities of heterotrophic plate count bacteria, while high levels of coliforms were detected only in iron tubercles. Coliform bacteria with the same biochemical profile were found both in distribution system biofilms and in the water column. Assimilable organic carbon determinations showed that carbon levels declined as water flowed through the study area. Maintenance of a 1.0-mg/liter free chlorine residual was insufficient to control coliform occurrences. Flushing and pigging the study area was not an effective control for coliform occurrences in that section. Because coliform bacteria growing in distribution system biofilms may mask the presence of indicator organisms resulting from a true breakdown of treatment barriers, the report recommends that efforts continue to find methods to control growth of coliform bacteria in pipeline biofilms.

Examination and characterization of distribution system biofilms.

Pure cultures of Escherichia coli, Klebsiella pneumoniae, Enterobacter aerogenes, and Citrobacter freundii were injured ( greater than 90%) in water from a dead-end section of the Bozeman, Montana, distribution system. The effects of the following laboratory variables on the enumeration efficiency of injured and undamaged control cells were examined: (i) diluent composition, temperature, and time of exposure; (ii) media, using various formulations employed in enumerating gram-negative bacteria; and (iii) surface pore morphology of membrane filters. The addition of peptone or milk solids to diluents and low temperature (4 degrees C) maximized the recovery of injured cells, but had little effect on undamaged cells. Control cells were recovered with high efficiencies on most media tested, but recoveries of injured cells ranged from 0 to near 100%. Most of the media commonly used in water analysis recovered less than 30% of injured cells. This was explained in part by the sensitivity of injured bacteria to deoxycholate concentrations greater than 0.01%, whereas control cells were unaffected by 0.1%. Membrane filter surface pore morphology (at 35 degrees C) had a negligible effect on total coliform recoveries. Recommendations are made regarding procedures to improve the recovery of injured coliforms by routine laboratory practices.

Influence of diluents, media, and membrane filters on detection fo injured waterborne coliform bacteria.

Low levels of copper in chlorine-free distribution water caused injury of coliform populations. Monitoring of 44 drinking water samples indicated that 64% of the coliform population was injured. Physical and chemical parameters were measured, including three heavy metals (Cu, Cd, and Pb). Copper concentrations were important, ranging from 0.007 to 0.54 mg/liter. Statistical analyses of these factors were used to develop a model to predict coliform injury. The model predicted almost 90% injury with a copper concentration near the mean observed value (0.158 mg/liter) in distribution waters. Laboratory studies with copper concentrations of 0.025 and 0.050 mg/liter in an inorganic carbon buffer under controlled conditions of temperature and pH caused over 90% injury within 6 and 2 days, respectively. Studies of the metabolism of injured Escherichia coli cells indicated that the respiratory chain is at least one site of damage in injured cells.

Evidence for the role of copper in the injury process of coliform bacteria in drinking water. [Escherichia coli]

Evidence for the role of copper in the injury process of coliform bacteria in drinking water.

A new membrane filter medium was developed for the improved recovery of injured coliforms from drinking water. The new medium, termed m-T7, consists of 5.0 g of Difco Proteose Peptone no. 3, 20 g of lactose, 3.0 g of yeast extract, 0.4 ml of Tergitol 7 (25% solution), 5.0 g of polyoxyethylene ether W-1, 0.1 g of bromthymol blue, 0.1 g of bromcresol purple, and 15 g of agar per liter of distilled water. Additional selectivity may be obtained by aseptically adding 0.1 microgram of penicillin G per ml to the medium after autoclaving. In laboratory studies, m-T7 agar recovered 86 to 99% more laboratory-injured coliforms than did m-Endo agar. m-T7 agar also recovered an average of 43% more verified coliforms from 67 surface and drinking water samples than did the standard m-Endo membrane filter technique. From drinking water, m-T7 agar recovered nearly three times more coliforms than did m-Endo agar. Less than 0.5% of the colonies on m-T7 agar gave false-negative reactions, whereas greater than 70% of the typical yellow colonies from m-T7 agar produced gas in lauryl tryptose broth. Most of the verified coliforms isolated on m-T7 agar belonged to one of the four common coliform genera: Escherichia, 17.6%; Klebsiella, 21.7%; Citrobacter, 17.3%; Enterobacter, 32.2%. The results demonstrate that m-T7 agar is superior to m-Endo agar, especially for the isolation of injured coliforms from drinking water.

S C Cameron

Papers

Influence of diluents, media, and membrane filters on detection fo injured waterborne coliform bacteria.

Evidence for the role of copper in the injury process of coliform bacteria in drinking water. [Escherichia coli]

Evidence for the role of copper in the injury process of coliform bacteria in drinking water.

New medium for improved recovery of coliform bacteria from drinking water.